JP7185519B2 - Thermosetting resin filler, cured product thereof, and multilayer printed wiring board - Google Patents

Description

The present invention relates to a thermosetting resin filler, and more particularly, a plurality of wiring layers laminated in the thickness direction via insulating layers and through holes formed in the thickness direction of the plurality of wiring layers. Alternatively, a thermosetting resin filler, a cured product, and a multilayer printed wiring that can be suitably used for filling a multilayer printed wiring board having a recess having a bottom and a conductive portion and an insulating portion on the through hole or the inner wall of the recess Regarding the board.

2. Description of the Related Art As electronic devices become smaller and more sophisticated, there is a demand for finer patterns on printed wiring boards, smaller mounting areas, and higher density mounting of components. For this reason, double-sided boards with through-holes for forming interlayer connections for electrically connecting different wiring layers, insulating layers and conductor circuits are sequentially formed on a core material, and via holes and the like are used. A multi-layer substrate such as a build-up wiring board in which layers are connected and multi-layered is used. Then, area array mounting such as BGA (Ball Grid Array) and LGA (Land Grid Array) is performed.

In such a printed wiring board, recesses between conductor circuits on the surface, and holes such as through holes and via holes having wiring layers formed on the inner wall surfaces are filled with a thermosetting resin filler. is common. As the thermosetting resin filler, a thermosetting resin filler containing an epoxy resin as a thermosetting resin component, an epoxy resin curing agent, and an inorganic filler is generally used. For example, Patent Document 1 proposes a thermosetting resin filler containing a liquid epoxy resin, a liquid phenol resin, a curing catalyst, and two types of fillers as a thermosetting resin filler having excellent filling properties. It is

By the way, in recent years, as printed wiring boards have become more sophisticated, frequency characteristics have been improved by removing excess portions of the plated film on the walls of through holes and via holes that are not related to conduction between layers. It is For example, Patent Literature 2 proposes a printed wiring board provided with a hole formed by drilling a through hole or a via hole halfway using a method called a back drilling method. Further, Patent Document 3 proposes providing a plated film only on a part of the wall surface of a through hole or a via hole.

JP 2001-019834 A Japanese Patent Publication No. 2007-509487 JP 2012-256636 A

In the through-holes of printed wiring boards as described in Patent Documents 2 and 3, a plating film or the like is not formed on a part of the inner wall surface of the hole, or a part of the plating film is removed. , there are portions where the insulating layer of the printed wiring board is exposed. When a hole such as a through-hole having such a structure is filled with a thermosetting resin filler to fill the hole, the filler that contacts the inner wall surface of the hole forms a portion that contacts the plating film and a portion that contacts the insulating layer. will be The insulating layer of the printed wiring board is made of a resin material such as epoxy resin, and the plating film is made of a metal material such as copper. Therefore, when a filling material is used to fill the holes, the adhesion of the filling material differs between the insulating layer and the plating film due to the difference in material, and as a result, when filling the through holes with the above structure, etc. However, there is a problem that the adhesion between the inner wall surface and the filler differs depending on the position of the inner wall surface of the hole, and in some cases, the filler peels off or cracks occur. In particular, as in Patent Documents 2 and 3, the tendency is remarkable when the inner wall of the hole has a conductive portion and an insulating portion. In addition, by adopting a structure in which an insulating portion is provided as in Patent Documents 2 and 3, electrical insulation is also required. Thus, a thermosetting resin filler suitable for filling the through-holes having the structure described above while maintaining electrical insulation, which is the original purpose of the filler, has not yet been found.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermosetting resin filler that exhibits high adhesion to both conductive and insulating parts, suppresses the occurrence of cracks, and has excellent electrical insulation. In particular, a plurality of wiring layers stacked in the thickness direction via an insulating layer, a through hole or a recess having a bottom formed in the thickness direction of the plurality of wiring layers, and an inner wall of the through hole or the recess An object of the present invention is to provide a thermosetting resin filler which is excellent in the above characteristics when used for filling holes in a multilayer printed wiring board having a conductive portion and an insulating portion. Another object of the present invention is to provide a cured product formed using the thermosetting resin filler and a multilayer printed wiring board having the cured product.

As a result of intensive research, the inventors of the present invention have found that in the multilayer printed wiring board as described above, the filling state near the interface between both the conductive portion and the insulating portion and the filler is extremely poor. That is, after the filling state, specifically, filling the hole or recess with the filling material, it is difficult to maintain the filling state. It was found that gaps are likely to occur, and that such gaps cause poor adhesion of the filler. In addition, the present inventors have found that in a thermosetting resin filler containing an epoxy resin, an epoxy resin curing agent, and an inorganic filler, an epoxy resin having a specific functional group as the epoxy resin and a specific curing agent as the epoxy resin curing agent. The inventors have found that by combining two types of curing agents having a temperature, it is possible to realize a filling material that has high adhesion to both the conductive portion and the insulating portion and is also excellent in electrical insulation.

Furthermore, the inventors of the present invention have found that by using the two specific epoxy resins and the two specific curing agents as described above in combination, the adhesion to both the conductive part and the insulating part is high, Even when filling holes in a multilayer printed wiring board having a structure in which an insulating part is exposed on a part of the conductive part on the inner wall surface of the recess or hole, cracks can be suppressed and electrical insulation is also achieved. It was found that an excellent filler can be realized. The present invention is based on such findings.

That is, the thermosetting resin filler of the present invention is
including an epoxy resin, an epoxy resin curing agent and an inorganic filler,
The epoxy resin includes an epoxy resin having a tertiary amine and an epoxy resin having a bisphenol skeleton,
The epoxy resin curing agent contains at least two curing agents, one curing agent having an activation temperature of 60° C. or more and less than 130° C. and the other curing agent having an activation temperature of 130° C. or more in curing the epoxy resin. It is something to do.

In an embodiment of the present invention, the epoxy resin having a tertiary amine and the epoxy resin having a bisphenol skeleton may be contained in a mass ratio of 20:80 to 90:10.

In an embodiment of the present invention, the epoxy resin having a bisphenol skeleton may have at least one skeleton selected from the group consisting of bisphenol A type, bisphenol F type and bisphenol E type. .

Further, in an embodiment of the present invention, the epoxy resin having a bisphenol-type skeleton may contain at least two of an epoxy resin having a bisphenol-A-type skeleton and an epoxy resin having a bisphenol-F-type skeleton.

Further, in an embodiment of the present invention, the epoxy resin curing agent may be substantially free of solid epoxy resin.

In an embodiment of the present invention, the curing agent having an activation temperature of 60° C. or more and less than 130° C. and the curing agent having an activation temperature of 130° C. or more are in a ratio of 1:99 to 99:1 on a mass basis. may be included in

In an embodiment of the present invention, the curing agent having an activation temperature of 60° C. or more and less than 130° C. is at least one selected from the group consisting of 2-ethyl-4-methylimidazole and 2-methylimidazole. It may be a reaction product of an imidazole compound and a liquid epoxy compound.

Further, in an embodiment of the present invention, the inorganic filler may be at least one selected from the group consisting of calcium carbonate, silica, barium sulfate and aluminum oxide.

Further, in an embodiment of the present invention, the inorganic filler may have an average particle size of 0.1 μm to 15 μm.

Furthermore, a cured product according to another aspect of the present invention is a cured product of the thermosetting resin filler.

A multilayer printed wiring board according to another aspect of the present invention has the cured product.

ADVANTAGE OF THE INVENTION According to this invention, the adhesiveness to both an electroconductive part and an insulating part is high, the generation|occurrence|production of a crack can be suppressed, and the filler which is excellent in electrical insulation can be implement|achieved. In particular, a plurality of wiring layers stacked in the thickness direction via an insulating layer, a through hole or a recess having a bottom formed in the thickness direction of the plurality of wiring layers, and an inner wall of the through hole or the recess It can be realized when used for filling holes in a multilayer printed wiring board including a conductive portion and an insulating portion. Moreover, according to another aspect of the present invention, it is possible to realize a cured product formed using the thermosetting resin filler and a multilayer printed wiring board having the cured product.

It is the schematic explaining the process of filling the through-hole of a printed wiring board using a thermosetting resin filler. It is the schematic explaining the process of filling the through-hole of a printed wiring board using a thermosetting resin filler. It is the schematic explaining the process of filling the through-hole of a printed wiring board using a thermosetting resin filler. It is the schematic explaining the process of filling the through-hole of a printed wiring board using a thermosetting resin filler. 1 is a schematic cross-sectional view showing an embodiment of a printed wiring board filled with a thermosetting resin filler; FIG. FIG. 4 is a schematic cross-sectional view showing another embodiment of a printed wiring board filled with a thermosetting resin filler; FIG. 4 is a schematic cross-sectional view showing another embodiment of a printed wiring board filled with a thermosetting resin filler;

First, a method of filling a hole or the like by applying the thermosetting resin filler of the present invention to a general printed wiring board will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating a process of filling a through hole of a printed wiring board with a thermosetting resin filler. First, a printed wiring board 1 having through holes 4 with plated inner wall surfaces is prepared (FIG. 1a). A printed wiring board 1 as shown in FIG. 1a is prepared by forming a through-hole with a drill or the like in the surface of an insulating layer 6 on which a wiring layer 5 is provided, and electroless bonding is performed on the inner wall of the through-hole 4 and the surface of the wiring layer. A plated or electrolytically plated one can be preferably used.

Next, the through holes 4 are filled with a thermosetting resin filler. As a filling method, a mask having openings in the through holes is placed on the printed circuit board, and the thermosetting resin filler is applied through the mask by a printing method or the like, or by a dot printing method or the like. A method of filling the through holes with a thermosetting resin filler can be used. Thereafter, the printed wiring board 1 is heated to pre-cure the filled thermosetting resin filler (FIG. 1b). Pre-curing generally refers to a state in which the reaction rate of the epoxy resin is 80% to 97%. The pre-curing is preferably performed by first pre-curing the thermosetting resin filler at a relatively low temperature and then secondary pre-curing at a higher temperature than the primary pre-curing. By performing precuring in this manner, unnecessary portions of the precured material 7 protruding from the surface of the printed wiring board 1 can be easily removed by physical polishing, as described later, and a flat surface can be obtained. The hardness of the pre-cured product 7 can be adjusted by changing the heating time and heating temperature for pre-curing.

Subsequently, unnecessary portions of the pre-cured material 7 protruding from the surface of the through-hole are removed by polishing to flatten (FIG. 1c). Polishing can be suitably performed by a belt sander, buffing, or the like.

Next, after subjecting the surface of the printed wiring board 1 to pretreatment by buffing or roughening treatment as necessary, an outer insulating layer 8 is formed (FIG. 1d). Due to this pretreatment, the surface of the wiring layer 5 becomes a roughened surface having an excellent anchoring effect, so that it has excellent adhesion to the outer insulating layer 8 . The outer insulating layer 8 is a solder resist layer (not shown), an insulating resin layer (not shown), a protective mask (not shown), or the like, depending on the treatment to be performed thereafter. It can be formed by applying a curable resin composition such as a curable resin composition or a photocurable or thermosetting resin composition, or by laminating a dry film or a prepreg sheet. When forming a fine pattern on the outer insulating layer 8, it is preferable to use a photocurable or thermosetting resin composition or a dry film thereof.

After that, the printed wiring board 1 is heated to perform final curing (finish curing) to form the outer insulating layer 8 . When a photocurable or thermosetting resin composition is used to form the outer insulating layer 8, it is dried (temporarily cured), exposed to light, and then fully cured according to a known method. When a double-sided board as shown in FIG. 1A is used as the printed wiring board 1, the formation of the wiring layer 5 and the formation of the insulating layer 6 are alternately repeated by a well-known method. A multilayer printed wiring board can also be formed by forming through holes 3 accordingly.

FIG. 2 is a schematic cross-sectional view showing one embodiment of a multilayer printed wiring board filled with a thermosetting resin filler. A multilayer printed wiring board 1 to which a thermosetting resin filler is applied has a plurality of wiring layers 20a, 20b, 20c, and 20d made of a plating film or the like laminated in the thickness direction with an insulating layer 10 interposed therebetween. The wiring layers 20a, 20b, 20c, and 20d are provided with through holes 40 (holes filled with a thermosetting resin filler) formed in the thickness direction. A conductive portion 20e extending from the wiring layer 20d is formed on the inner wall of the through hole 40 at one end of the hole portion of the through hole 40. As shown in FIG. At the other end of the hole portion of the through hole 40, the inner diameter of the through hole is enlarged so as to partially remove the wiring layer 20a after the conductive portion 20e is formed, and the insulating layer is exposed on the inner wall of the hole portion. Thus, the insulating portion 10a is formed. That is, the inner wall of the through-hole 40 (hole) is in a state of having the conductive portion 20e and the insulating portion 10a. By providing the conductive portion 20e and the insulating portion 10a on the inner wall of the through hole 40 (hole portion) in this manner, a portion that is not electrically connected is formed, and as a result, the transmission efficiency is improved. The through hole 40 (hole portion) having such a cross-sectional shape is filled with a thermosetting resin filler, and the filling is performed by heating and curing. In the present embodiment, the term "insulating layer" refers to a layer that supports a wiring layer while providing insulation between different wiring layers, and the term "wiring layer" refers to a layer that provides electrical continuity through a circuit. Further, the insulating portion means a portion where each layer is not electrically connected, and may include the insulating layer described above. On the other hand, the conductive portion means a portion such as a plated film for electrically conducting each wiring layer, and may include the wiring layer described above. Further, the through-hole refers to a hole provided so as to penetrate the entire thickness direction of the multilayer printed wiring board. The through holes need only be formed in the thickness direction of the wiring layer, and more specifically, should not be formed parallel to the wiring layer. In the present embodiment, the wiring layer extending on the wall surface of the through hole is used as the conductive portion, but the wiring layer partially exposed on the wall surface of the through hole is also referred to as the conductive portion. In addition to the case where the above-mentioned wiring layer is formed by extending the wall surface, the case where a conductive film is formed on the wall surface by plating or the like is also referred to as a conductive portion.

In another embodiment of the present invention, the shape of the hole portion of the through hole may be different from that described above, for example, as shown in FIG. A multilayer printed wiring board having a structure in which a conductive portion 30e is formed by removing a portion of the conductive portion and an insulating layer is exposed to expose the conductive portion 30e and the insulating portion 10a. There may be. In the present embodiment, the wiring layer extending on the wall surface of the through hole is used as the conductive portion, but the wiring layer partially exposed on the wall surface of the through hole is also referred to as the conductive portion. In addition to the case where the above-mentioned wiring layer is formed by extending the wall surface, the case where a conductive film is formed on the wall surface by plating or the like is also referred to as a conductive portion.

Further, in another embodiment of the present invention, the holes to be filled with the thermosetting resin filler are not limited to the through holes. For example, as shown in FIG. 2 may be used. In multilayer printed wiring board 2, wiring layer 50a provided on one surface of insulating layer 10 extends to the wall surface and bottom portion 60 of recess 70 to form conductive portion 50d. The inner diameter of the recess is enlarged so that a part of the wiring layer 50a is removed after the formation, and the insulating layer 10a is formed on the inner wall of the hole by exposing the insulating layer. That is, the inner wall of the recess (hole) having a bottom is in a state of having the conductive portion 50d and the insulating portion 10a. In this embodiment, the wiring layer extending on the wall surface of the recess is used as the conductive portion, but the wiring layer partially exposed on the wall surface of the recess is also referred to as the conductive portion. In such a multilayer printed wiring board 2, when the recess 70 having the bottom 60 is filled with a thermosetting resin filler, both the conductive portion extending from the wiring layer 50a and the insulating portion exposed on the wall surface of the recess 70 comes into contact with the thermosetting resin filler. In addition to the case where the above-mentioned wiring layer is formed by extending the wall surface, the case where a conductive film is formed on the wall surface by plating or the like is also referred to as a conductive portion. In the present embodiment, the term "recess" refers to a portion of the surface of the multilayer printed wiring board that is clearly recessed from other portions.

In the multilayer printed wiring board, the inner diameter and depth of the through hole or the recess having the bottom are preferably 0.1 to 1 mm and 0.1 to 10 mm, respectively.

The wiring layer forming the conductive portion is not particularly limited, and may be copper plating, gold plating, tin plating, or the like. , preferably made of copper. Similarly, insulating layers constituting printed wiring boards include paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth/non-woven cloth epoxy, glass cloth/paper epoxy, synthetic fiber epoxy, fluorine-based resin, Polyphenylene ether, polyphenylene oxide, cyanate ester, polyimide, PET, glass, ceramics, silicon wafer and the like. Among these, glass cloth/non-woven epoxy, polyphenylene ether, polyimide, and ceramic are preferable from the viewpoint of the filling property of the thermosetting resin filler and the adhesion to the cured product, and those containing epoxy resin are preferable. A cured product is more preferred. The epoxy resin-containing cured product refers to a cured product of an epoxy resin impregnated with glass fibers or a cured product of a resin composition containing an epoxy resin.

The thermosetting resin filler of the present invention is used for filling holes in multilayer printed wiring boards having conductive portions and insulating portions on the inner walls of through holes or recesses as described above, and contains epoxy resin as an essential component. and an epoxy resin curing agent and an inorganic filler. Each component constituting the thermosetting resin filler of the present invention will be described below.

<Epoxy resin>
The thermosetting resin filler of the present invention contains, as essential components, two types of epoxy resins, an epoxy resin having a tertiary amine and an epoxy resin having a bisphenol skeleton. When the thermosetting resin filler contains these two types of specific epoxy resins, the filler has high adhesion to both the conductive portion and the insulating portion, and is excellent in electrical insulation. Although the reason for this is not clear, it is considered as follows. That is, in the present invention, by including an epoxy resin having a polar group such as a tertiary amine as the epoxy resin, the insulating portion is generally formed not only from an organic material such as an epoxy resin but also from a metal material. It is considered that the filling property of the filler is improved with respect to the member having both portions of the conductive portion. In addition, it is believed that the inclusion of an epoxy resin having a bisphenol-type skeleton can reduce the water absorption of the cured product, resulting in improved electrical insulation. Furthermore, the combination of the epoxy resin having a bisphenol-type skeleton and the epoxy resin having a tertiary amine makes it possible to maintain the filling state of the filler at a high level. Adhesion can be improved. However, the above mechanism is only speculation by the present inventors, and is not necessarily bound by this theory.

The epoxy resin having a tertiary amine is not particularly limited as long as it has two or more epoxy groups in one molecule and has a tertiary amine group. It may be a family-based epoxy resin. From the viewpoint of heat resistance, electrical insulation, water absorption, etc., aromatic epoxy resins are preferable to aliphatic epoxy resins. Further, the epoxy resin having a tertiary amine may be liquid, semi-solid or solid, and liquid is preferred. In the present invention, the term "liquid" refers to the state of liquid having fluidity at 20°C.

Liquid epoxy resins having a tertiary amine as described above include tetraglycidylaminodiphenylmethane, tetraglycidylmetaxylylenediamine, triglycidyl-para-aminophenol, diglycidylaniline, diglycidylorthotoluidine and the like. Examples of solid materials include diaminodiphenylmethane type epoxy and the like. These epoxy resins having a tertiary amine may be used singly or in combination of two or more. These commercial products include Mitsubishi Chemical Corporation jER630 (para-aminophenol type epoxy resin), jER604 (diaminodiphenylmethane type epoxy), Sumitomo Chemical Co., Ltd. ELM-100 (para-aminophenol type epoxy resin), Nippon Kayaku Co., Ltd. GAN (diglycidylaniline) manufactured by Nippon Kayaku Co., Ltd., GOT (diglycidylorthotoluidine) manufactured by Nippon Kayaku Co., Ltd., and the like.

Examples of the epoxy resin having a bisphenol skeleton include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E (AD) type epoxy resin, bisphenol S type epoxy resin and the like. And from the viewpoint of adhesion to insulating parts, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol E (AD) type epoxy resin are preferable. The epoxy resin having a bisphenol skeleton may be liquid, semi-solid, or solid, but liquid is preferred from the viewpoint of filling properties. The liquid state is as described in the explanation of the epoxy resin having a tertiary amine. These epoxy resins having a bisphenol skeleton may be used singly or in combination of two or more. In particular, two types of bisphenol A type epoxy resin and bisphenol F type epoxy resin are used in combination. is preferred. These commercial products include Mitsubishi Chemical Corporation jER828, jER834, jER1001 (bisphenol A type epoxy resin), jER807, jER4004P (bisphenol F type epoxy resin), Air Water R710 (bisphenol E type epoxy resin) and the like.

The epoxy resin having a tertiary amine and the epoxy resin having a bisphenol skeleton are preferably contained in a ratio of 20:80 to 90:10 on a mass basis, and are contained in a ratio of 20:80 to 60:40. is more preferable. If the ratio of the two is within the above range, the filler can be even more excellent in electrical insulation and excellent in adhesion to the conductive portion and the insulating portion.

The thermosetting resin filler of the present invention may contain epoxy resins other than those described above, and within a range that does not impair the effects of the present invention, for example, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A Novolak type epoxy resin, biphenyl type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, phosphorus-containing Epoxy resins, anthracene-type epoxy resins, norbornene-type epoxy resins, adamantane-type epoxy resins, fluorene-type epoxy resins, alkylphenol-type epoxy resins, and the like may be included. The epoxy resin described above is preferably liquid at room temperature from the viewpoint of hole-filling properties. However, epoxy resins that are solid at room temperature are not excluded. An epoxy resin that is solid at room temperature may be dissolved and used. From the viewpoint that the effect of the present invention is exhibited more effectively, it is preferable that the epoxy resin does not substantially contain a solid epoxy resin. In the present specification, "substantially free of solid epoxy resin" does not mean that the content of solid epoxy resin in the filler is strictly 0% by mass. This is intended to allow the content up to 5% by mass.

<Epoxy resin curing agent>
The thermosetting resin filler of the present invention contains, as an essential component, the epoxy resin curing agent for curing the epoxy resin described above, and the epoxy resin curing agent has an active temperature of 60° C. to 130° C. in curing the epoxy resin. At least two curing agents are used: a curing agent having a temperature lower than 100° C. and a curing agent having an activation temperature of 130° C. or higher. Commonly used known curing agents for curing epoxy resins include, for example, amines, imidazoles, polyfunctional phenols, acid anhydrides, isocyanates, and polymers containing these functional groups. However, in the present invention, two types of curing agents having different curing temperature ranges, which will be described later, are used in combination with the above-described two types of specific epoxy resins to improve adhesion to both the conductive portion and the insulating portion. It is possible to obtain a filler that has a high resistance, can suppress the occurrence of cracks, and has excellent electrical insulation. Although the reason for this is not clear, it is considered as follows. That is, it is presumed that the rapid curing reaction can be suppressed by adding two kinds of curing agents having different curing temperatures. As a result, it is possible to improve both the occurrence of cracks and the electrical insulation while improving the adhesion to both the insulating portion and the conductive portion. However, the above mechanism is only speculation by the present inventors, and is not necessarily bound by this theory.

Examples of the curing agent having an activation temperature of 60° C. or more and less than 130° C. that are used in combination with the above-described two specific epoxy resins include polyamines, imidazole adducts, specific imidazole compounds, and the like. Polyamines include polyalkylenepolyamines having 2 to 6 carbon atoms, adduct compounds of aliphatic polyamines such as aromatic ring-containing aliphatic polyamines having 8 to 15 carbon atoms, isophoronediamine, and 1,3-bis(aminomethyl). Preferably, the main component is an alicyclic polyamine adduct compound such as cyclohexane, or a mixture of the above-mentioned aliphatic polyamine adduct compound and the above-mentioned alicyclic polyamine adduct compound. In particular, a curing agent containing an adduct compound of xylylenediamine or isophoronediamine as a main component is preferred. In the present specification, the activation temperature is a sample (filler (composition)) measured at a temperature elevation of 5° C./min using a differential scanning calorimeter (DSC8500, manufactured by PerkinElmer Co., Ltd.). shall mean the temperature of the peak top at the time of measurement.

As the adduct compound of the aliphatic polyamine, those obtained by subjecting the aliphatic polyamine to addition reaction with aryl glycidyl ether (especially phenyl glycidyl ether or tolyl glycidyl ether) or alkyl glycidyl ether are preferable. Moreover, as the adduct compound of the alicyclic polyamine, those obtained by subjecting the alicyclic polyamine to addition reaction with n-butyl glycidyl ether, bisphenol A diglycidyl ether or the like are preferable.

Aliphatic polyamines include alkylenediamines having 2 to 6 carbon atoms such as ethylenediamine and propylenediamine, polyalkylenepolyamines having 2 to 6 carbon atoms such as diethylenetriamine and triethylenetriamine, and aromatic ring-containing fats having 8 to 15 carbon atoms such as xylylenediamine. group polyamines. Examples of commercially available modified aliphatic polyamines include FXE-1000, Fujicure FXR-1020, Fujicure FXR-1030, Fujicure FXR-1080, FXR-1090M2 (manufactured by Fuji Kasei Kogyo Co., Ltd.), Ancamine 2089K, Sunmide P- 117, Sunmide X-4150, Ancamine 2422, Serwet R, Sunmide TX-3000, Sunmide A-100 (manufactured by Air Products Japan Co., Ltd.) and the like.

Examples of alicyclic polyamines include isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane, and lalomine. Commercially available modified alicyclic polyamines include, for example, Ancamine 1618, Ancamine 2074, Ancamine 2596, Ancamine 2199, Sunmide IM-544, Sunmide I-544, Ancamine 2075, Ancamine 2280, Ancamine 1934, and Ancamine 2228 (Air Products Japan Co., Ltd.). Company), Daito Kural F-5197, Daito Kural B-1616 (manufactured by Daito Sangyo Co., Ltd.), Fuji Cure FXD-821, Fuji Cure 4233 (manufactured by Fuji Chemical Industry Co., Ltd.), jER Cure 113 (manufactured by Mitsubishi Chemical Corporation), and Lalomin C-260 (manufactured by BASF).

As the imidazole adduct, an adduct of an imidazole compound and an epoxy compound can be preferably used. Examples of the epoxy compound used as the adduct include those obtained by reacting an epoxy resin such as bisphenol A type with imidazole. The term “liquid” has the same definition as above. Examples of imidazole compounds include 2-methylimidazole, 4-methyl-2-ethylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, and 2-ethylimidazole. , 2-isopropylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, etc. Among these, 2- Ethyl-4-methylimidazole and 2-methylimidazole are preferably used. Examples of commercially available imidazole adducts include Amicure PN-23, Amicure PN-23J, Amicure PN-H, Amicure PN-31, Amicure PN-31J, Amicure PN-40, Amicure PN-40J, and Amicure PN-50. , Amicure PN-F, Amicure MY-24, Amicure MY-H (both manufactured by Ajinomoto Fine Techno Co., Ltd.), P-0505, L-07N, L-07E (both manufactured by Shikoku Chemical Industry Co., Ltd.), P- 200 (manufactured by Mitsubishi Chemical Corporation), ADEKA HARDNER EH-5001P, ADEKA HARDNER EH-5057PK, ADEKA HARDNER EH-5030S, ADEKA HARDNER EH-5011S (all manufactured by ADEKA Corporation), and the like. Further, as a curing agent having an activation temperature of 60° C. or more and less than 130° C. other than the above, for example, specific imidazole compounds such as 2E4MZ, C11Z, 2PZ, and 2MZ-H (all of which are manufactured by Shikoku Kasei Kogyo Co., Ltd.) are used. can be mentioned.

In addition, as a curing agent having an activation temperature of 130° C. or higher, which is used in combination with two specific types of epoxy resins, a specific imidazole compound can be suitably used, specifically 2,4-diamino -6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine, 2,4-diamino-6-(2'ethyl-4'-methylimidazolyl-(1'))-ethyl-s-triazine, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxylmethylimidazole and the like. Examples of commercially available products that can be suitably used as a curing agent having an activation temperature of 130° C. or higher include 2MZ-A, which is an azinated product of 2MZ; 2E4MZ-A, which is an azinated product of 2E4MZ; 2P4MHZ (all manufactured by Shikoku Kasei Co., Ltd.) and the like.

The blending ratio of the curing agent having an activation temperature of 60° C. or more and less than 130° C. and the curing agent having an activation temperature of 130° C. or more is the amount of the epoxy resin curing agent. From the viewpoint of adhesion, suppression of crack generation, electrical insulation, water absorption, etc., the range is preferably 1:99 to 99:1, and preferably 30:70 to 70:30 on a mass basis. more preferred.

In addition, the total amount of the two types of epoxy resin curing agents described above is determined from the viewpoint of adhesion to both the conductive part and the insulating part, shape retention, filling, crack generation suppression, electrical insulation, water absorption, etc. Therefore, it is preferably 1 to 30 parts by mass, more preferably 4 to 20 parts by mass, per 100 parts by mass of the epoxy resin.

The epoxy resin curing agent may contain conventionally known epoxy resin curing agents other than the above as long as the effects of the present invention are not impaired. For example, amines such as dicyandiamide and diaminodiphenylmethane, hydroquinone, resorcinol, Examples include polyfunctional phenols such as bisphenol A, halogen compounds thereof, and condensates of these with aldehydes such as novolac and resole resins. Acid anhydrides include phthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, benzophenonetetracarboxylic acid and the like. Examples of isocyanates include tolylene diisocyanate and isophorone diisocyanate, and these isocyanates may be masked with phenols or the like.

<Inorganic filler>
The thermosetting resin filler of the present invention contains an inorganic filler for stress relaxation due to cure shrinkage of the filler and adjustment of the coefficient of linear expansion. As the inorganic filler, known inorganic fillers used in ordinary resin compositions can be used. Specifically, non-metals such as silica, barium sulfate, calcium carbonate, silicon nitride, aluminum nitride, boron nitride, alumina, magnesium oxide, aluminum hydroxide, magnesium hydroxide, titanium oxide, mica, talc, and organic bentonite. Examples include fillers and metal fillers such as copper, gold, silver, palladium, and silicone. One type of these inorganic fillers may be used alone, or two or more types may be used in combination.

Among these inorganic fillers, calcium carbonate, silica, barium sulfate, and aluminum oxide, which are excellent in low hygroscopicity and low volume expansion, are preferably used, and among these, silica and calcium carbonate are more preferably used. Silica may be amorphous, crystalline, or a mixture thereof. Amorphous (fused) silica is particularly preferred. Calcium carbonate may be either natural heavy calcium carbonate or synthetic precipitated calcium carbonate.

The shape of the inorganic filler is not particularly limited, and includes spherical, needle-like, plate-like, scale-like, hollow, irregular, hexagonal, cubic, and flaky shapes. A spherical shape is preferable from the point of view.

The average particle size of these inorganic fillers is preferably 0.1 μm to 25 μm, preferably 0.1 μm to 25 μm, taking into account the dispersibility of the inorganic filler, the ability to fill holes, and the smoothness when a wiring layer is formed in the filled portion. A range of 0.1 μm to 15 μm is suitable. More preferably, it is 1 μm to 10 μm. The average particle size means the average primary particle size, and the average particle size (D50) can be measured by a laser diffraction/scattering method.

The blending ratio of the inorganic filler is 10 to 1000 parts by mass with respect to 100 parts by mass of the epoxy resin, from the viewpoint of achieving both the thermal expansion coefficient, polishability, and adhesiveness of the cured product, as well as printability and hole-filling properties. parts, more preferably 20 to 500 parts by mass, and particularly preferably 30 to 300 parts by mass.

<Other ingredients>
To the thermosetting resin filler of the present invention, a filler treated with a fatty acid or amorphous filler such as organic bentonite or talc can be added to impart thixotropy.

The above fatty acid has the general formula: (R1COO) _n —R2 (substituent R1 is a hydrocarbon having 5 or more carbon atoms, substituent R2 is hydrogen, a metal alkoxide, or a metal, and n is 1 to 4). Compounds represented can be used. The fatty acid can exhibit the effect of imparting thixotropy when the substituent R1 has 5 or more carbon atoms. More preferably, n is 7 or more.

The fatty acid may be an unsaturated fatty acid having a double bond or triple bond in the carbon chain, or a saturated fatty acid containing no such. For example, stearic acid (the number of carbon atoms and the number of unsaturated bonds and the numbers in parentheses are represented by their positions. 18: 0), hexanoic acid (6: 0), oleic acid (18: 1 (9)), icosane acid (20:0), docosanoic acid (22:0), melissic acid (30:0) and the like. The substituent R1 of these fatty acids preferably has 5 to 30 carbon atoms. More preferably, it has 5 to 20 carbon atoms. Also, for example, a skeleton having a long fatty chain (having 5 or more carbon atoms) with a coupling agent structure, such as a metal alkoxide in which the substituent R2 is a titanate-based substituent capped with an alkoxyl group. There may be. For example, the product name KR-TTS (manufactured by Ajinomoto Fine-Techno Co., Inc.) can be used. In addition, metal soaps such as aluminum stearate and barium stearate (each manufactured by Kawamura Kasei Co., Ltd.) can be used. Other metal soap elements include Ca, Zn, Li, Mg and Na.

From the viewpoint of thixotropic property, embedding property, defoaming property, etc., the mixing ratio of the fatty acid is appropriately 0.1 to 2 parts by weight per 100 parts by weight of the inorganic filler.

The fatty acid may be added by using an inorganic filler surface-treated with a fatty acid in advance, and it becomes possible to more effectively impart thixotropy to the thermosetting resin filler. In this case, the blending ratio of the fatty acid can be lower than when the untreated filler is used. It is preferably 1 to 1 part by mass.

Further, the thermosetting resin filler of the present invention may contain a silane coupling agent. By adding a silane-based coupling agent, it is possible to improve the adhesion between the inorganic filler and the epoxy resin and suppress the occurrence of cracks in the cured product.

Silane-based coupling agents include, for example, epoxysilane, vinylsilane, imidazolesilane, mercaptosilane, methacryloxysilane, aminosilane, styrylsilane, isocyanatesilane, sulfidesilane, and ureidosilane. Also, the silane coupling agent may be blended by using an inorganic filler that has been surface-treated with a silane coupling agent in advance.

The mixing ratio of the silane-based coupling agent should be 0.05 to 2.5 parts by mass with respect to 100 parts by mass of the inorganic filler from the viewpoint of achieving both adhesion and defoaming properties between the inorganic filler and the epoxy resin. is preferred.

The thermosetting resin filler of the present invention may optionally contain an oxazine compound having an oxazine ring obtained by reacting a phenol compound, formalin and a primary amine. By containing the oxazine compound, after curing the thermosetting resin filler filled in the holes of the printed wiring board, when performing electroless plating on the formed cured product, it is possible to use an aqueous solution of potassium permanganate or the like. It facilitates the roughening of the cured product and improves the peel strength of the plating.

In addition, known colorants such as phthalocyanine blue, phthalocyanine green, disazo yellow, titanium oxide, carbon black and naphthalene black, which are used in ordinary screen printing resist inks, may be added.

In addition, known thermal polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, tert-butyl catechol, pyrogallol, and phenothiazine for imparting storage stability during storage, and clay, kaolin, and the like for viscosity adjustment. Known thickeners and thixotropic agents such as organic bentonite and montmorillonite can be added. In addition, known additives such as silicone-based, fluorine-based, polymer-based antifoaming agents, leveling agents, imidazole-based, thiazole-based, triazole-based, silane coupling agents, and other adhesive agents are added. be able to. In particular, when organic bentonite is used, the portion protruding from the surface of the hole portion is easily formed into a protruding state that is easy to polish and remove, and is excellent in polishability, which is preferable. In addition, known and commonly used colorants such as phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, crystal violet, titanium oxide, carbon black, naphthalene black, etc., can also be blended.

The viscosity of the thermosetting resin filler measured by a rotary viscometer is preferably 200 to 1000 dPa·Sec at 25° C. and 5 rpm for 30 sec. With a viscosity within this range, both shape retention (suppression of liquid dripping) and embedding properties can be further improved. More preferably, it is 200 to 800 dPa·Sec. The viscosity is measured by a cone-plate viscometer consisting of a cone rotor (cone rotor) and a plate described in JIS Z 8803, for example, TV-30 type (manufactured by Toki Sangyo, rotor 3° × R9.7). measured.

The thermosetting resin filler of the present invention can be formed by using a known patterning method such as a screen printing method, a roll coating method, a die coating method, or a vacuum printing method. It fills a recess with a bottom. At this time, it is completely filled so as to protrude slightly from the hole or recess. By heating a multilayer printed wiring board in which holes and recesses are filled with a thermosetting resin filler, for example, at 80 to 160° C. for about 30 to 180 minutes, the thermosetting resin filler is cured and a cured product is obtained. It is formed. In particular, from the viewpoint of suppressing the generation of outgassing, it is preferable to perform curing in two stages. That is, it is preferable to pre-cure the thermosetting resin filler at a lower temperature, and then to perform main curing (finish curing). Heating at 80 to 110° C. for about 30 to 90 minutes is preferable as the condition for pre-curing. Since the hardness of the pre-cured cured product is relatively low, the unnecessary portion protruding from the substrate surface can be easily removed by physical polishing, and the surface can be flattened. After that, it is heated to be fully cured. Heating at 130 to 160° C. for about 30 to 180 minutes is preferable as the condition for main curing. At this time, the cured product hardly expands or contracts due to its low expansibility, and the final cured product is excellent in dimensional stability, low hygroscopicity, adhesion, electrical insulation and the like. The hardness of the pre-cured product can be controlled by changing the heating time and heating temperature for pre-curing.

After forming a cured product by curing the thermosetting resin filler as described above, unnecessary portions of the cured product protruding from the surface of the printed wiring board are removed by a known physical polishing method and planarized. After that, the surface wiring layer is patterned into a predetermined pattern to form a predetermined circuit pattern. If necessary, the surface of the cured product may be roughened with an aqueous solution of potassium permanganate or the like, and then a wiring layer may be formed on the cured product by electroless plating or the like. A printed wiring board having the cured product of the present invention is formed by the method described above. From the viewpoint of further solving the problems of the present invention, among printed wiring boards, a multilayer printed wiring board, in particular, a plurality of wiring layers laminated in the thickness direction via an insulating layer, and the plurality of wirings A multilayer printed wiring board is preferably provided with a through hole formed in the thickness direction of the layer or a recess having a bottom, and a conductive portion and an insulating portion on the inner wall of the through hole or the recess.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the following description, "parts" and "%" are based on mass unless otherwise specified.

<Preparation of thermosetting resin filler>
Various components shown in Tables 1 and 2 below were blended in the proportions (parts by mass) shown in each table, premixed with a stirrer, and then dispersed with a three-roll mill, Examples 1 to 10 and Comparative Examples. Thermosetting resin fillers 1-7 were prepared. When the viscosity of each thermosetting resin filler obtained was measured using a viscometer (manufactured by Toki Sangyo Co., Ltd., model TV-30, rotor 3° × R9.7), 25 ° C., 5 rpm 30 Sec value was in the range of 300 to 500 dPa·Sec under the measurement conditions.

Note that *1 to *16 in Table 1 represent the following components.
*1: Mitsubishi Chemical Corporation jER630 (triglycidylaminophenol, liquid)
*2: ELM-100 (para-aminophenol type liquid epoxy resin) manufactured by Sumitomo Chemical Co., Ltd.
*3: GAN (diglycidylaniline, liquid) manufactured by Nippon Kayaku Co., Ltd.
*4: GOT manufactured by Nippon Kayaku Co., Ltd. (diglycidyl orthotoluidine, liquid)
*5: Mitsubishi Chemical Corporation jER828 (bisphenol A type liquid epoxy resin)
*6: Mitsubishi Chemical Corporation jER807 (Bisphenol F type liquid epoxy resin)
*7: Air Water R710 (Bisphenol E type liquid epoxy resin)
*8: DEN431 manufactured by Dow Chemical Co. (phenol novolac type semi-solid epoxy resin)
* 9: 2PHZ (imidazole hydroxymethyl body) manufactured by Shikoku Kasei Co., Ltd.
* 10: 2E4MHZ (imidazole hydroxymethyl body) manufactured by Shikoku Kasei Co., Ltd.
* 11: Fuji Cure FXR-1030 (modified aliphatic polyamine) manufactured by Fuji Kasei Kogyo Co., Ltd.
* 12: jER cure 113 (modified aliphatic polyamine) manufactured by Mitsubishi Chemical Corporation
*13: Shikoku Kasei Co., Ltd. P-0505 (imidazole adduct)
*14: Bihoku Funka Kogyo Co., Ltd. Softon 1800 (calcium carbonate, average particle size 1.2 μm)
*15: ACEMATT3300 manufactured by Evonik Degussa Japan Co., Ltd. (amorphous silica, average particle size 9.5 μm)
*16: Shin-Etsu Chemical Co., Ltd. SK-66 (silicone oil)

<Evaluation>
(1) Evaluation of adhesion of filler (conductive portion) A wiring layer (plating thickness: 25 μm) made of copper plating was formed on the entire inner wall surface of a through hole with an inner diameter of 0.3 mm and a depth of 3.2 mm. A multilayer printed wiring board with a thickness of 3.2 mm having through holes is prepared, each thermosetting resin filler is filled in the through holes by screen printing, and placed in a hot air circulation drying oven (DF610 manufactured by Yamato Scientific Co., Ltd.). The thermosetting resin filler was cured by heating at 150° C. for 30 minutes. The cross section of the through-hole filled with the filler was observed with an optical microscope and an electron microscope, and evaluated according to the following criteria. In addition, in performing microscopic observation, the cross section of the through-hole to be observed was formed as follows. That is, a multilayer printed wiring board including through holes is cut perpendicular to the thickness direction, and the cut surface is coated with SiC polishing paper (manufactured by Marumoto Struers Co., Ltd., Nos. , FORCIPOL-2V) was used to polish the cross-section of the through-hole.
○: No separation between the conductive part (wiring layer) and the filler △: Slight separation between the conductive part (wiring layer) and the filler ×: Clear separation between the conductive part (wiring layer) and the filler The evaluation results were as shown in Tables 1 and 2 below.

(2) Evaluation of adhesion of filler (insulating part) A through-hole having an inner diameter of 0.5 mm was formed by a drill in a printed wiring board having a thickness of 3.2 mm in which the insulating layer was made of glass cloth/non-woven epoxy. With the insulating layer exposed on the inner wall surface, each thermosetting resin filler is filled in the through-hole by screen printing, and dried at 150°C for 30 minutes in a hot air circulation drying oven (DF610 manufactured by Yamato Scientific Co., Ltd.). The thermosetting resin filler was cured by heating. The cross section of the through-hole filled with the filler was observed with an optical microscope and an electron microscope, and evaluated according to the following criteria. The cross-section of the through-hole to be observed was performed in the same manner as in (1) Evaluation of adhesion of filler (conductive portion).
○: No peeling of the insulating part (insulating layer) and the filler △: Slight peeling of the insulating part (insulating layer) and the filler ×: Clear peeling of the insulating part (insulating layer) and the filler The evaluation results were as shown in Tables 1 and 2 below.

(3) Evaluation of adhesion of filler (conductive part / insulating part) (1) Drilling from one side to a depth of 1.6 mm (drill diameter 0.5 mm) to remove part of the wiring layer to expose the insulating layer, prepare a multilayer printed wiring board having a through hole in which a conductive portion and an insulating portion are formed on the inner wall, and apply heat to the through hole. The curable resin filler was filled by screen printing, and heated at 150° C. for 30 minutes in a hot air circulation drying furnace (DF610 manufactured by Yamato Scientific Co., Ltd.) to cure the thermosetting resin filler. The cross-section of the entire penetration filled with the filling material was observed with an optical microscope and an electron microscope, and evaluated according to the following criteria. The cross section of the through-hole to be observed was polished in the same manner as in (1) Evaluation of adhesion of filler (conductive portion).
◎: No peeling of the filler from both the conductive part and the insulating part ○: Slight peeling of the filler from either the conductive part or the insulating part △: Both the conductive part and the insulating part Separation from the filler ×: Clear separation from the filler on both the conductive portion and the insulating portion The evaluation results were as shown in Tables 1 and 2 below.

(4) Confirmation of Filling State The following evaluation was performed on the filling state of the filler into the through holes. That is, (1) drilling from one side to a depth of 1.6 mm (drill diameter 0.5 mm) to remove part of the wiring layer to expose the insulating layer, prepare a multilayer printed wiring board having a through hole in which a conductive portion and an insulating portion are formed on the inner wall, and apply heat to the through hole. A curable resin filler was filled by screen printing, and the substrate was placed on a rack to maintain an angle of 90°±10° and left at room temperature for 30 minutes. The state after leaving was visually confirmed. Judgment criteria are as follows.
A: The filled state is maintained.
◯: Slight collapse was observed, but there was no dent on the through-hole surface.
x: The filling state was disturbed, and dents were observed on the through-hole surfaces.
The evaluation results were as shown in Tables 1 and 2 below.

(5) Water absorption evaluation The thermosetting resin filler of each example and comparative example was applied to the glossy side (copper foil) of GTS-MP foil (manufactured by Furukawa Circuit Foil Co., Ltd.) with an applicator, and hot air circulation type It was cured at 150° C. for 30 minutes in a drying oven (DF610 manufactured by Yamato Scientific Co., Ltd.). After that, the cured product was peeled off from the copper foil, and the sample was cut into a measurement size (50 mm x 50 mm size), dried at 100 ° C. for 2 hours, and the moisture was completely removed. W1) was measured. After that, the sample was immersed in distilled water controlled at 23° C.±2° C., and the mass (W2) was measured after 24 hours. The water absorption rate was determined by (W2-W1)/W1 x 100 (%).
Water absorption evaluation was performed according to the following criteria.
◎: Water absorption less than 1.0% ○: Water absorption 1.0% or more and less than 1.5% △: Water absorption 1.5% or more and less than 2.0% ×: Water absorption 2.0% or more Evaluation results was as shown in Tables 1 and 2 below.

(6) Electrical insulation evaluation On the FR-4 substrate on which IPC-B-25A comb-shaped electrodes described in IPC-SM-840-D are formed, the thermosetting resin filler of each example and comparative example is applied. The thermosetting resin filler is cured by printing with a screen printing method and heating at 150°C for 30 minutes in a hot air circulation drying oven (DF610 manufactured by Yamato Scientific Co., Ltd.) to form a cured product pattern and provide insulation. An evaluation board for resistance measurement was produced. The insulation resistance value of the obtained evaluation substrate was measured under the following conditions and used as an initial value. As for the initial value, it was confirmed that the insulation resistance of any sample was 1.0×10 ¹² Ω or more. After that, IPC-SM-840-D ClassH (25 to 65°C ± 2°C cycle, humidity 90% +3%, -5%, VDC = 50V, measurement time 100V, T = 160h, D coupon, 500 MΩ or more ) was measured under the following conditions.
Insulation resistance measurement conditions:
DC 100V was applied to the evaluation board, and the insulation resistance value was measured. The insulation resistance value after the treatment was evaluated according to the following criteria.
◎: Insulation resistance of 1.0×10 ¹¹ Ω or more ○: Insulation resistance of less than 1.0×10 ¹¹ Ω, 1.0×10 ¹⁰ Ω or more △: Insulation resistance of less than 1.0×10 ¹⁰ Ω, 1 0×10 ⁹ Ω or more ×: Insulation resistance is less than 1.0×10 ⁹ Ω The evaluation results were as shown in Tables 1 and 2 below.

(7) Crack evaluation (1) Drilling (drill diameter 0.5 mm) to a depth of 1.6 mm from one side of the multilayer printed wiring board used in the evaluation of the adhesion of the filler (conductive part) and part of the wiring layer is removed to expose the insulating layer, prepare a multilayer printed wiring board having a through hole in which a conductive portion and an insulating portion are formed on the inner wall, and fill the through hole with each thermosetting resin filler by screen printing Then, the thermosetting resin filler was cured by heating at 150° C. for 30 minutes in a hot air circulation drying furnace (DF610 manufactured by Yamato Scientific Co., Ltd.). The cross section of the through-hole filled with the filler was observed with an optical microscope and an electron microscope, and evaluated according to the following criteria. The cross section of the through-hole to be observed was polished in the same manner as in (1) Evaluation of adhesion of filler (conductive portion).
○: No cracks observed △: Slightly small cracks observed ×: One or more large cracks observed The evaluation results were as shown in Tables 1 and 2 below.

As is clear from the evaluation results in Tables 1 and 2, two types of epoxy resins, an epoxy resin having a tertiary amine and an epoxy resin having a bisphenol skeleton, were cured at an activation temperature of 60°C or more and less than 130°C. Thermosetting resin fillers (Examples 1 to 10) using two types of epoxy resin curing agents, a curing agent and a curing agent with an activation temperature of 130 ° C. or higher, have good adhesion to both the conductive part and the insulating part, and In addition to excellent crack resistance and excellent electrical insulation properties, the above two specific epoxy resin curing agents are added to either an epoxy resin having a tertiary amine or an epoxy resin having a bisphenol skeleton. The thermosetting resin filler (Comparative Examples 1 to 5) used in combination has excellent adhesion of the conductive part or the insulating part, but the filling state and crack resistance are worse than those of the examples, and the conductive part and the insulating part It can be seen that the adhesion to both is poor. It is also found that the thermosetting resin fillers (Comparative Examples 1, 2, 4 and 5) that do not contain an epoxy resin having a bisphenol skeleton as the epoxy resin have low water absorption and poor electrical insulation.

In addition, a thermosetting resin filler (Comparative Example 6 ), and a thermosetting resin filler (Comparative Example 7) using only an epoxy curing agent with an activation temperature of 60 ° C. or more and less than 130 ° C. has excellent adhesion to both the conductive part and the insulating part, and It can be seen that although the insulating properties are excellent, the crack resistance is inferior.

REFERENCE SIGNS LIST 1 printed wiring board 2 multilayer printed wiring board having through-holes 3 multilayer printed wiring board having recesses 4 through-holes with plated inner wall surfaces 5 wiring layer 6 insulating layer 7 precured material 8 outer insulating layer 10 insulating layer 10a insulating portion 20a, 20b, 20c, 20d wiring layers 30a, 30b, 30c, 30d wiring layers 40 through holes 50a, 50b, 50c, wiring layers 20e, 30e, 50d conducting portions 60 bottoms 70 recesses

Claims (9)

containing an epoxy resin, an epoxy resin curing agent and an inorganic filler,
The epoxy resin contains an epoxy resin having a tertiary amine and an epoxy resin having a bisphenol skeleton,
The epoxy resin having a bisphenol-type skeleton includes at least two types of an epoxy resin having a bisphenol-A-type skeleton and an epoxy resin having a bisphenol-F-type skeleton,
The epoxy resin curing agent contains at least two curing agents, one curing agent having an activation temperature of 60° C. or more and less than 130° C. and the other curing agent having an activation temperature of 130° C. or more in curing the epoxy resin. A thermosetting resin filler. 2. The thermosetting resin filler according to claim 1, wherein the epoxy resin having a tertiary amine and the epoxy resin having a bisphenol skeleton are contained in a mass ratio of 20:80 to 90:10. 3. The thermosetting resin filler of claim 1 or 2 , wherein the epoxy resin is substantially free of solid epoxy resin. Claims 1 to 3, wherein the curing agent having an activation temperature of 60°C or more and less than 130°C and the curing agent having an activation temperature of 130°C or more are contained in a mass ratio of 1:99 to 99: 1 . A thermosetting resin filler according to any one of the preceding claims. A reaction product of at least one imidazole compound selected from the group consisting of 2-ethyl-4-methylimidazole and 2-methylimidazole and a liquid epoxy compound, wherein the curing agent whose activation temperature is 60° C. or more and less than 130° C. The thermosetting resin filler according to any one of claims 1 to 4 . The thermosetting resin filler according to any one of claims 1 to 5 , wherein the inorganic filler is at least one selected from the group consisting of calcium carbonate, silica, barium sulfate and aluminum oxide. The thermosetting resin filler according to any one of claims 1 to 6 , wherein the inorganic filler has an average particle size of 0.1 µm to 15 µm. A cured product of the thermosetting resin filler according to any one of claims 1 to 7 . A multilayer printed wiring board comprising the cured product according to claim 8 .

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